A method of measuring refractive indices of gases by observations of Rayleigh scattered light is described. The method depends on the fact that the intensity of such scattered light is proportional to the square of the refractivity of the gas. Results are presented for several gases at a wavelength of 1216 Å. The values are placed on an absolute basis by use of the value of the refractive index of nitrogen found at 1220 Å by the Črenkov method. Some extensions of the method are suggested.
P. GILL and D. W. O. HEDDLE, "Determination of the Refractive Indices of Gases in the Vacuum Ultraviolet. II. The Rayleigh Scattering Method," J. Opt. Soc. Am. 53, 847-851 (1963)